So I have an idea for a dungeon crawl, where the dungeon has been sealed for over 150 years...

There are also Inter-Planar beacons, located within the Dungeon, so the possibility of creatures from the material planes are also possible...

What creatures can i use, my party are Lvl 9, of which there is 3 

The core requirement is monsters that are one of the following

1. Able and willing to just sit around for 150 years waiting for PCs. This usually means constructs or undead. Note the NPC stat blocks section in chapter 9 of the DMG gives rules for skeleton and zombie templates.
2. Held in some form of suspended animation. This does mean that careful PCs can probably avoid activating them, as they're effectively traps. If you want to bother with a mechanic, one option is glyph of warding to cast greater restoration on the victim of flesh to stone. This lets you include pretty much any monster that's vulnerable to those spells.
3. Summoned at need. This limits you to summonable creature types, which mostly means celestials, elementals, fey (including fey beasts), and fiends.

Perhaps an entire hidden civilisation of monsters has grew in that dungeon for the past 150 years, you could use a series of deurgars or drows. As a challenge maybe you could throw in a dire troll, or a HUGE mimic (increase the statblock damage, hp, etc to your liking). 
Like Pantagruel666 said, zombies and skeletons are a great way of emphasising how old this dungeon is.

Good luck with your campaign!

how about:

The beacons you mentioned are inter-planar alarms. The dungeon is actually a vault where Githyanki pirates hide their loot as well as a place to raise some Dragons. As the party enter the dungeon the Githyanki on the Astral Plane are made aware of their intrusion and send out some of their members to get rid of the interlopers. The party can come across these pirates with some draconic allies, namely Red Chromatic Guard Drakes. In additon to this there is a Slumbering Young Red Dragon in the hear tof the dungeon that the pirates are raising, they use the material plane ot do this as creatures do not age in the Astral Plane so its the only way to get a Dragon to mature.

Add in Dragon lair actions and whatever mundane traps you feel comfy with and you have a somewhat literal Dungeon and Dragons adventure. There can be lots of loot to find, Githyanki using Misty Step shennigans to hit and run and keep the party on their toes.

I have written a few dungeons recently that were lost for centuries.  I agree with the above, you are stuck with: constructs, undead, monsters that are magically summoned when triggered, or monsters that naturally reproduce and die over time (I used spiders for my island campaign.  After 300 years, they had overrun large parts of the island)

I try to avoid the "monster smoking a cigarette'" if possible (ie a monster that sits in a room for no good reason for long periods of time, just waiting to be killed by a PC).  

Quote from Velstitzen >>

I have written a few dungeons recently that were lost for centuries.  I agree with the above, you are stuck with: constructs, undead, monsters that are magically summoned when triggered, or monsters that naturally reproduce and die over time (I used spiders for my island campaign.  After 300 years, they had overrun large parts of the island)

I try to avoid the "monster smoking a cigarette'" if possible (ie a monster that sits in a room for no good reason for long periods of time, just waiting to be killed by a PC).  

 Yes but also no?  You can skin any monster to seem like it could have lasted for centuries you just have to describe them as seeming undead, robotic  or magical. That last one, magical is also a big category already. Things like aberrations, fiends, elementals, celestials and fey can be said to haunt locations for millennia, its really only giants, plants, humanoids and beasts which you typically wouldn't find in a sealed tomb.   If you  really want one of those categories you can also work around it with things  like having creatures in suspended animation e.g frozen as a statue. 

monster smoking a cigarette cracked me up so hard I made my husband pause his movie to read it to him. Well done.

Yeah, undead and constructs are good, but what if it's an underground, ancient laboratory used for experiments by a cult, or maybe to breed supersoldiers for an ancient war. Tanks of liquid with abberations or something in them, and the beacons are a last ditch defense in case of assault. Zombie cultists? Maybe mummies, I love mummies. Anyway, in that context, the creatures in the tanks might be friendly, or at least willing to talk, and you could give the monsters adventure hooks by the monsters telling the adventurers about the past (they have been locked away for 150 years, opens possibilites for more ancient dungeons)

This made me think of the old, old Lucasarts game called "The Dig" which has a part with a dead, desiccated guard monster which, when a trap is triggered, has a "indistinguishable-from-magic" crystal fall from a slot onto the corpse and revived it. That, or something similar could be a neat way to handle enemies of a different type, just as long as you don't let players get their hands on any of that magic.

There is quite a lot of selection ... any creature that could live that long and be bound in some way.

Constructs and Undead were mentioned.

Devils and Demons could both be bound with spells or deals to perform a task in the dungeon and can't leave.

Elementals could naturally inhabit the area or be bound to it for some reason.

Elves - elves live long enough if there is food and water available.

Aberrations - far realm creatures, beholders or beholderkin, almost anything whose reasons for what they might choose to do could be considered inscrutable.

Depending on the creatures, you might need to provide a source of nourishment but there are lots of ways to do that.

You could even have a dragon lair at the bottom with a subterranean lake that connects to a labyrinth of flooded caves with an exit through a surface lake miles away. Black dragons are amphibious so the bottom level of a hidden/lost temple once occupied by a dragon cult might make for a decent home :)

The real question isn’t what to populate it with, it’s how has it been populated? Is there a bbeg actively populating it ala Halaster and undermountain? Is it some ancient evil locked away with guardians and traps? Is it an old abandoned complex/mine/???  That has had creatures come in from both above and below and developed its own distinct “ecology”? Once you have the how, the what is far easier.

Molds, slimes, and aliens.

Some real life creatures can stay dormant for hundreds of years.